The present invention relates to a device for controlling a drive motor of a motorized roller blind consisting of stackable slats, said device comprising an automatic control reacting to a variation in the drive torque.
It is known, from a relatively large number of documents and installations in operation, to measure the drive torque and control the stopping of the motor as a result of a comparison of the measured torque with a reference value.
The device described in the patent application DE 196 10 877, the content of which is incorporated by reference, uses a torsion bar acting on two strain gauges, for example piezoelectric sensors. The device described in the patent application EP 0 822 316, the content of which is incorporated by reference, uses a spring which opposes the rotation of the housing of the motor, this rotation being detected by optical sensors or an angular displacement sensor In the device according to the patent EP 0 703 344, the content of which is incorporated by reference, the torque value thresholds are determined by two springs which oppose the rotation of the housing of the motor, said rotation acting directly on two switches controlling the feed of the motor. When the roller blind is being wound up, the motor is stopped, after the blind has executed a predetermined travel, from the moment when the torque has reached the threshold determined by the corresponding spring.
In the case of a single-phase asynchronous motor with a phase shifting capacitor, it is known to use one or two operating parameters of the motor in order to determine the torque threshold. It has been proposed, for example, to use the voltage measured at the terminals of the phase shifting capacitor (DE-A-27 26 696, DE-C-31 30 035, the contents of which are incorporated by reference) or the starting voltage on the winding of the motor, which is compared with the feed voltage (U.S. Pat. No. 4,196,462, the content of which is incorporated by reference) or the voltage at the terminals of the auxiliary winding of the motor or else the phase shift of the currents in the main winding and in the auxiliary winding.
All the known devices require a setting which depends on the dimensions and weight of the roller blind, on the method of fastening it to the winding tube and on the conditions of its installation, in particular the amount by which it is unwound. As regards the type of fastening of the roller blind to its winding tube, this fastening may be ensured, in particular, by means of metal foil, a strap or a bolt. The settings will be different, depending on the fitting of the roller blind and its type of fastening to its winding tube. In particulars if the roller blind is fastened to its winding tube by means of metal foil, that is to say a steel leaf forming a spring, when the slats of the roller blind are fully stacked the winding tube will have an elastic play which will result in a relatively slow variation in the drive torque. By contrast, if this fastening is ensured by means of a strap, the torque will temporarily remain zero until the roller blind is rewound in the opposite direction, whilst if the fastening is ensured by means of a bolt, that is to say is rigid, the torque will increase abruptly under the same conditions.
It is known to dispense with these settings by causing the automatic control to learn the torque curve of the motor after installation. In this case, if the motor is removed in order to be installed in another winding tube, a new learning procedure is necessary Aging of the installation and the change in the friction forces may also make a new learning process necessary, in order once again to obtain complete closing or opening of the roller blind. Therefore, what is needed is a cut-off algorithm which dispenses with the setting and learning processes.
The control device according to the invention is defined in that its automatic control comprises means for identifying the type of end travel associated with the type of fastening of the roller blind, said means operating by analyzing the variation in the drive torque, and means for adapting the control of the stopping of the motor to the type of end travel identified.
On the basis of the analysis of the variation in the drive torque, that is to say of the curve representing this variation, the automatic control is thus capable of recognizing whether the roller blind is being wound up or, on the contrary, whether the slats are being stacked up. If the blind is being wound up, the control device can simply stop the motor when the variation in the drive torque exceeds a particular value corresponding to the arrival of the last slat of the roller blind at its upper limit. By contrast, if the automatic control has identified that the slats are being stacked up, it can initiate a special procedure for analyzing the trend of the drive torque, in order to identify the type of connection of the apron of the roller blind to its winding tube and to control the stopping of the motor according to special criteria adapted to each type of fastening.
For this purpose, the automatic control preferably comprises a logical processing unit ( less than  less than LPU greater than  greater than ) containing a program for analyzing the variation in the drive torque, according to which program it is determined whether the roller blind is in the winding or unwinding or stacking or unstacking phase, the detected state is recorded, the detection of a state different from the recorded state is awaited, this different state is recorded, and the type of end of travel is determined by analyzing the sequence of the two recorded states.
If the automatic control has recognized that the roller blind is in the stacking phase, the logical processing unit, after detecting the cancellation of the drive torque corresponding to the end of stacking of the slats, analyzes, by means of a subprogram, the trend of the drive torque, starting from zero: if the torque remains zero for a predetermined time, this corresponding to strap fastening, or if the torque changes relatively slowly from zero, this corresponding to fastening by metal foil, the automatic control immediately interrupts the power to the motor. By contrast, if the torque increases rapidly, signifying rigid bolt fastening, the automatic control interrupts the power to the motor when the variation in the drive torque reaches a predetermined value, as usually occurs when the roller blind arrives at its upper limit.
In the event that the LPU has identified an xe2x80x9cunstacking/windingxe2x80x9d sequence, a rapid and continuous increase in the torque is detected and the stopping of the motor is controlled when the variation in the torque exceeds a predetermined value. Stopping could also be controlled with a delay, as described in the patent EP 0,703,344.